Tennis and the like playing balls



Patented Aug. 8, 1933 1,921,108 TENNIS AND THE LIKE PLAYING BALLS Douglas Frank Twiss, Wylde. Green, Birmingham,

Albert Edward Toney Neale, Ward End, Birmingham,

and 7 Albert Stanley Carpenter,

Walmley, Birmingham, England," assignors to Dunlop Rubber Company, Limited,

ham, England, a British Corporation Application February 28, 1933, 659,025, and in Great Britain March No Drawing.

Serial No. 7 1, 1932 This invention has reference to permanently sealed inflated objects particularly tennis and the like playing balls, which are dependent upon an inflation value.

On account of the permeability ofthe envelopes of these objects, particularly when composed of rubber, and the diffusion therethrough of the gas used'for inflation, the internal pressure may gradually decrease and sooner or later, the loss of pressure may become so great that the objects can be rendered useless for their intended purpose. 1

Hitherto efforts to prevent this loss of pressure have been directed mainly to treatment applied from the exterior of the object, sometimes With damage to the envelope, but in any case only producing a temporary eilect.

The aim, of this invention is to provide for a constancy of internal pressure in objects of the kind set forth, preferably without puncturing or in any other way damaging the envelope of the structure.

According tothis invention, the inflation value in permanently sealed objects, particularly tennis and the like playing balls, which is impaired by permeability. of the envelope, is maintained or rehabilitated by providing for an indefinitely continuous generation of gas at an appropriate rate inside the object.

For this purpose we embody within the object, either forming a constituent of the envelope of he object itself, or placed within the envelope, known substance or substances capable of gencrating gas, preferably at a rate consistent with the speed of escape of the gas by diffusion through the envelope, so as to make good the normal loss of inflation gas and prevent the loss of pressure which would otherwise occur.

Generally speaking, the invention comprises the use of known substance or substances which naturally liberategas either alone or in consequence of reaction with other agents.

The gas generating substance or substances agent also may constitute a normal constituent of the envelope or it may be provided specially for the purpose, and may conveniently be water or Birming- 12 Claims. (01. .27361) an aqueous solution for example of a suitable acidic or alkaline chemical compound.

I Substances suitable for the purpose may comprise or be composedof metals such as aluminum, inc, cadmium, magnesium and iron, or com,- pounds such ascalcium hydride, aluminum carbide or the like, and are preferably employed in a powdered or disintegrated form. A mixture of barium peroxide and manganese dioxide may also be used or a mixture or compound of urea with an acid such as oxalic acid.

As previously stated themetal or other substance; or substances may be actually blended in the material-0f the envelopaor may be'placed inside the envelope before or after vulcanization.

W e prefer, however, to distribute the substance or substances over the inner surface of the object and effect attachment thereto by' any suitable means, as for example by incorporation in a material of colloid character such as a gelatinous or rubber layer which is built into or uponthe inner surface of theobjectduring manufacture.

In the caseof playing balls afmeth'od of uniplying it or them locally at one or more positions.

In the case where the generation of gas is dependent on the chemical interaction of the substance or substances with an agent such as water or an aqueous solution inside the ball, the rate of migration or penetration of the agent into the medium containing the gas-generating substance or substances will be an important factor in determining the rate of generation of the gas for the maintenance of the inflation pressure.

The rate of generation of the gas can be adjusted by varying the proportion and amount of gas generating substance or substances and/ or of the additional agent if such be employed.

When gelatin, or say a gelatin-glycerin jelly is used as a supporting medium, the rate of generation may further be adjusted by altering the hydrogen-ion concentration of the jelly or of the liquid in contact with it, and if the gas generating material be in a rubber medium the rate of evolution of gas may be preadjusted by suitable compounding of the medium, e. g. by adjusting the proportion of gas-generating substance or 'substances to rubber, or by the incorporation of suitable proportions of wax, carbon black, zinc oxide,

Aluminum carbide sulphur or any other compounding ingredient or by varying the degree of vulcanization of the rubber medium which may affect the reactivity of the substance or substances and also the rate of ingress of the chemical agent (e. g. water or aqueous solution from the inside of the structure).

In the case of aluminum carbide methane is generated, and in other instances for example aluminum or zinc, hydrogen is the gas evolved. In the case of a mixture of barium peroxide and manganese dioxide oxygen is generated. In the case of urea and oxalic acid, with an aqueous solution of sodium nitrite inside the ball, nitrogen is generated.

An example of a substance capable of naturally liberating gas alone is hydrogen peroxide which can be introduced into a tennis ball subsequent to its vulcanization by for example a hypodermic needle.

As rubber or the like is a substance commonly employed for the envelope, it willbe appreciated that the incorporation of the substance or substances in the rubber will present no difficulties which cannot be easily overcome.

; A suitable rubber medium containing gas-generating substance to be applied to the inner surface of the object and to generate gas by the action of a small quantity of water in the interior of the ball is as follows:

i Parts by weight Rubber 100 Mercaptobenzthiazole 1. 3

Sulphur -l 3 Zinc oxide 5 Stearic acid 1 This rubber mixture can be vulcanized and in contact with water generates gas at a suitable rate,

What we claim is:

1. A method for maintaining or rehabilitating the inflation value in permanently sealed objects, particularly tennis and the like playing balls, which is impaired by permeability of the envelope, which comprises continuously generating gas at a rate inside the object of substantially the same magnitude as the rate of gas loss therefrom .by embodying within the object a substance or equal to the rate of gas loss therefrom.

2. A method of providing gaseous pressure in an enclosure having flexible walls that are not perfectly impermeable, which comprises embodying within the object a substance or substances capable of generating gas at a rate equal to the rate of gas loss therefrom.

3. A method as claimed in claim 2, wherein the substance or substances capable of generating gas are those which naturally liberate gas alone.

4; A method as claimed in claim 2, wherein the substance or substances capable of generating gas are those which generate gas in consequence of reaction with other agents.

5. A method as claimed in claim 2, wherein the gas generating substance or substances are embodied within the material with which the envelope is constructed.

6. A method as claimed in claim 2, wherein the gas generating substance or substances are independently applied.

'7. A method as claimed in claim 2, wherein the gas generating substance is aided by an agent forming a normal constituent of the object.

8. A method as claimed in claim 2, wherein the gas generating substances comprise or are composed-of reagents of the group consisting of aluminium, zinc, cadmium," magnesium, iron, calcium hydride, or aluminium carbide.

9. A method as claimed in claim 2, wherein the substances are employed in a powdered or disintegrated condition. a

10. A method as claimed in claim 2, wherein the gas forming substance or substances are distributed over the inner surface of the object and attachment effected thereto by any suitable means.

11. A rubber walled enclosure having its interior filled with gas under pressure and a "substance therein to evolve gases at a rate substantially the same as that of loss by leakage through the walls of said container. v

12. A rubber walled enclosure having its interior filled with gas under pressureand a substance on the inner surface evolving gas at atmospherictemperatures at a rate substantially that at which gas passes through the walls of said enclosure.

' DOUGLAS FRANK TWISS.

ALBERT EDWARD TONEY NEALE. ALBERT STANLEY CARPENTER. 

